The present invention claims the benefit of Japanese Patent Application No. 2000-314086, filed Oct. 13, 2000, the entirety of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a valve gear for an internal combustion engine, wherein one side of the engine includes at least two poppet valves. The valve gear includes a rocker arm having a bifurcated end for driving the at least two poppet valves.
2. Description of Background Art
A conventional valve gear for a 4-stroke cycle internal combustion engine is known, wherein one suction or exhaust valve is driven to open and close through a rocker arm from a camshaft. The other of the suction or exhaust valve is directly driven to open and close from the camshaft (Japanese Patent Application Laid-Open No. 5-133207 Publication).
In the aforementioned valve gear, three suction poppet valves and two exhaust poppet valves are disposed per cylinder. A camshaft is provided with five cam crests per cylinder corresponding 1:1 to each poppet valve. Top ends of the three suction poppet valves are placed in contact with three cam crests of the camshaft to be directly driven to open and close by the cam crests. The other two exhaust poppet valves are driven to open and close by two cam crests of the camshaft through respective rocker arms. Therefore, many cam crests are necessary, two rocker arms are necessary to avoid the ignition plug, the number of parts increases, and the construction becomes complex. Accordingly, there is a disadvantage in terms of productivity and costs.
The present invention relates to an improvement in a valve gear of an internal combustion engine, which overcomes the above drawbacks. In an internal combustion engine, at least one side of the engine includes not less than two poppet valves. A valve gear includes a rocker arm formed with a bifurcated end which crosses an ignition plug on the valve side having not less than two poppet valves. The other valve is directly driven to open and close from a camshaft.
With the above construction according to the present invention, with regard to the poppet valves on the side driven to open and close by the rocker arm, one cam crest is sufficient and one rocker arm is sufficient. Furthermore, the number of assembling steps is reduced, the valve gear is decreased in weight, the construction is simplified, the productivity is enhanced considerably, and lower cost is achieved.
Furthermore, since the rocker arm is bifurcated or branched into the shape of a U to avoid the ignition plug, a nipping angle between one poppet valve and the other poppet valve is small, a combustion chamber enabling higher compression and higher combustion efficiency is easily constructed, and the performance of the internal combustion engine is materially enhanced.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.